In a computing environment, a Virtual Machine Monitor (VMM) is a software program that can present a virtualized physical machine interface on top of which multiple Operating Systems, including unmodified user applications, can be run. A virtual machine may be an instance of an operating system that executes on the VMM. Virtual machines may be used to concurrently run two or more different operating systems on a single physical computer system, for example, to isolate test and beta versions of computer program modules, without affecting other systems on a computer system. Further, virtual machines may be used to separate storage on a computer system, in order to create isolated storage systems.